The present invention relates to endoscopic devices and in particular to a fiberoptic having a single fiber light guide which has a ring shaped core with a hollow cylindrical central channel along its length.
The transmission of light through thin fibers of glass or plastics have permitted a variety of instruments for the visualization of otherwise inaccessible organs and tissues inside the human body. Such instruments are broadly referred to as endoscopes and have been useful in the diagnosis and treatment of, for example, gastrointestinal and respiratory diseases.
In recent years, thin, flexible optical fibers have allowed for the remote viewing, photography, biopsy and surgery of organs and tissues. Such thin, flexible optical fibers, also known as fiberoptics, are incorporated in endoscopes to enable the transmission of light to illuminate the internal space being viewed and for enabling the object so illuminated to be viewed. Generally, the viewing capability is accomplished by aligning multiple fibers so that the relative position of each fiber is the same at each end of the bundle. The methods and apparatus for transmitting images therealong is well-known and need not be discussed further.
In addition to light and image transmission, endoscopes frequently have auxiliary channels through which fluids can pass, either from or to the observation site, and by which implements and tools can be remotely controlled. In addition to the above, fiberoptics are used in guiding laser radiation for applications in surgery, fluorescence methods of diagnosis and high intensity illumination. The fiberoptics in endoscopes have also been applied to the development of a variety of transducers for the measurement and monitoring of parameters such as blood flow, temperature, pressure and the like.
Recent developments have involved the use of fiberoptics in an endoscope known as a cardioscope to allow for visualization of intracardial structures. This field, better known as angioscopy, may be defined as the technique for visualization of the inner surfaces of blood vessels by means of the cardioscope. Since its introduction, advances in the use of the cardioscope have enabled the fiberoptics to be inserted into arteries and vessels to enable visualization. A flexible fiberoptic scope has also be recently used to beam laser energy and to observe orifices in the coronary arteries of patients.
Because of these advances in the application of endoscopes, there is a continuing need to develop fiberoptics of very small diameter which are nevertheless capable of performing all of the above described functions. Typical endoscopes presently include a bundle of fiberoptics each having a light transmitting core and an outer cladding. The light enters the end of the core and is reflected by the cladding so as to pass down the core to the other end. A multiplicity of such fiberoptics may be gathered together into a bundle along which light passes to illuminate the object at the distal end of the endoscope. A second bundle, arranged in a coherent manner, may also be incorporated to provide a means of viewing the illuminated area at the distal end of the endoscope. Various other channels may be provided for the transmission of fluids, the control of miniature tools or surgical instruments or any other desired function. The illuminating bundle, the visualizing bundle and the auxiliary channels are gathered together in a multi-lumen or hollow cylindrical sheath. The sheath necessarily has a thickness which increases the thickness and bulkiness of the endoscope, often preventing its use in smaller vessels of the body. Therefore, it is desired to make an endoscope which has a decreased diameter to thereby increase the application of the endoscope in examining increasingly smaller blood vessels and for other uses as well.
Various constructions have been proposed for endoscopes. For example, endoscopes have been developed where the viewing bundle is centrally disposed with the illuminating bundle consisting of a multiplicity of optical fibers surrounding the central viewing bundle so that the viewing bundle and the illuminating bundle are in co-axial alignment. (See "Fiberoptics", Fiberoptics OISD Encyclo- pedia 1979 at page E-97 through E-99.) At the recent OFS proceedings in Presentation No. THASS2 entitled "Self-Imaging By Ring Core Fibers", page 123, OFS Thursday, Feb. 18 1985, Niemeier, Ulrich and Poole presented a multi-mode optical wave guide which incorporated a single mode ring core fiber.
However, heretofore there has still been no means of eliminating the sheath of the endoscope. The present invention provides a single optical fiber with a hollow center core through which a viewing bundle, one or more transport channels or any of the other devices used in endoscopes may be positioned and having a ring shaped cross-section around the central channel which ring-shaped section provides a light pathway for illuminating an object at the distal end of the endoscope. The ring-shaped cross-section core has cladding both on the inside and on the outside. Because the core is a single fiber, it can act as both a sheath and light guide allowing the conventional sheath tubing to be eliminated. The result is the reduction of the outer diameter of the elongated viewing portion of the device making it possible to visualize, for example, small blood vessels.
In the preferred embodiment, the hollow fiberoptic is made from plastic and has a hollow center cylindrical region through which a glass or plastic coherent bundle may be slidably received.
In an alternative embodiment, the hollow fiberoptic will be an integral part of the viewing structure. This can be accomplished by filling the preform of the hollow fiberoptic with multiple solid fiberoptics arranged in a coherent manner. When the resulting assembly is drawn through an oven, a structure is generated which contains a plastic coherent bundle surrounded by a single plastic hollow fiberoptic. Such a structure will have favorable physical characteristics with a substantially reduced manufacturing cost.
A particular advantage of the hollow fiberoptic is the existence of the central hollow channel which can be used, for example, to guide the hollow fiberoptic over a flexible guide wire which has been placed across an obstruction of a blood vessel to thereby be able to very precisely position the end of the fiberoptic adjacent a location predefined by a guide wire. Sliding the hollow fiberoptic over this guide wire allows safe guidance of this fiberoptic inside the blood vessel with a minimum risk of vessel perforation. Yet another application of the hollow fiberoptic in accordance with the invention is as a sensor which can again be guided over a guide wire into the vessel of choice. Finally, the central channel of the hollow fiberoptic in accordance with the invention could be used to deliver various solutions and medications into the body while performing diagnostic functions or therapeutic functions such as laser recanalization.
The present invention is particularly useful in performing laser recanalization. This procedure positions a coherent light bundle adjacent an obstruction in a vessel. Laser energy is then directed at the obstruction to vaporize and thereby eliminate the obstruction. A particularly serious problem using present endoscopes and techniques has been the inability to position the laser carrying coherent bundle so that it points at the obstruction and not at the sidewall of the vessel. If the laser is directed toward the vessel wall rather than the obstruction, the laser energy will perforate the vessel wall thereby greatly increasing the risk to the patient. It is therefore desired to provide an endoscope which will more accurately position a laser transporting coherent bundle so that it points at the obstruction rather than in another direction. The present invention substantially solves this positioning problem since the coherent bundle is held about its circumference in position by the single hollow fiberoptic which can be accurately positioned by sliding the single hollow fiberoptic over a flexible guide wire previously placed across the obstruction of the blood vessel.